The Doctrine\ODM\MongoDB\Id\AbstractIdGenerator class has been deprecated.
Custom ID generators must implement the Doctrine\ODM\MongoDB\Id\IdGenerator
interface.
The Doctrine\ODM\MongoDB\Mapping\ClassMetadata class has been marked final and
will no longer be extendable in 3.0.
The boolean, integer, and int_id mapping types have been deprecated. Use
the bool, int, and int types, respectively. These types behave exactly the
same.